Add null check for path (#346)

Author: John Reese

System.IO.Abstractions.TestingHelpers.Tests/MockFileInfoTests.cs

@@ -9,6 +9,17 @@ namespace System.IO.Abstractions.TestingHelpers.Tests
     [TestFixture]
     public class MockFileInfoTests
     {
+        [Test]
+        public void MockFileInfo_NullPath_ThrowArgumentNullException()
+        {
+            var fileSystem = new MockFileSystem();
+
+            TestDelegate action = () => new MockFileInfo(fileSystem, null);
+
+            Assert.Throws<ArgumentNullException>(action);
+
+        }
+
         [Test]
         public void MockFileInfo_Exists_ShouldReturnTrueIfFileExistsInMemoryFileSystem()
         {

System.IO.Abstractions.TestingHelpers/MockFileInfo.cs

@@ -11,7 +11,7 @@ public class MockFileInfo : FileInfoBase
         public MockFileInfo(IMockFileDataAccessor mockFileSystem, string path)
         {
             this.mockFileSystem = mockFileSystem ?? throw new ArgumentNullException(nameof(mockFileSystem));
-            this.path = path;
+            this.path = path ?? throw new ArgumentNullException(nameof(path));
         }
 
         MockFileData MockFileData